Specifies conditions under which Global Temporary Table data blocks (DBs) in fallback subtables will be compressed by default.
Compression is subject to the BlockLevelCompression field setting, and to the criteria specified by the MinPercentCompReduction and MinDBSectsToCompress DBS Control fields. DBs not meeting these minimum criteria will not be compressed.
Field Group
Compression
Valid Settings
| Setting | Description |
|---|---|
| ALWAYS | The DBs of a new table will be compressed regardless of Query Band options specified at load time. |
| ONLYIFQBYES | The DBs of a new table will not be compressed unless a Query Band used at load time specified to compress them. |
| UNLESSQBNO | The DBs of a new table will be compressed unless a Query Band used at load time specified not to compress them. |
| NEVER | The DBs of a new table will not be compressed regardless of any Query Band used at load time. The Ferret utility COMPRESS command will have no effect. |
Default
NEVER
Changes Take Effect
After the DBS Control Record has been written.
Usage Notes
BLC enables data compression at the data block (DB) level of the file system. Compression reduces the amount of storage required for a given amount of data. The BlockLevelCompression field of DBS Control enables and disables BLC.
BLC can be enabled or disabled system-wide, or for various categories of tables. For Permanent data, these include subtables for primary, fallback, eligible LOB data, and join and hash indexes. Secondary indexes on primary rows and fallback copies of secondary indexes are never compressed.
Related Information
| For more information on... | See... |
|---|---|
| BlockLevelCompression field | BlockLevelCompression. |
| COMPRESS and UNCOMPRESS commands | Ferret Utility (ferret). |
| BLOCKCOMPRESSION query band | Teradata Vantage™ - SQL Data Definition Language Syntax and Examples, B035-1144. |